1. Field of the Invention
This invention relates to the method and means for enhancing human visual perception of a moving object, and particularly to spectacles equipped with optical shutters that function to enhance the ability of the human visual physiology to track the path of an object moving at high speed.
2. Description of the Prior Art
This invention is an improvement on the method and apparatus of the following United States patents relating to the use of optical shutter spectacles to control the level of ambient brightness perceived by the human eye through the spectacles:
Belgorod 4,279,474
Humphrey 5,276,539
U.S. Pat. No. 4,279,474 discloses a method and apparatus for controlling the level of brightness perceived by the human eye by using spectacles that operate as a variable duty cycle electronically controlled shutter. The shutter frequency is maintained above the flicker fusion frequency of the human eye to achieve a perceived continuous image of reduced brightness. U.S. Pat. No. 5,276,539, issued to the inventor of the instant invention, discloses a method and apparatus for nodalizing a spectacle lens and independently controlling the light transmission through a selected node or nodes in response to the ambient brightness in that nodal portion of the field of view.
The accurate and timely perception of motion of a moving object in relation to its surroundings, or vice versa, is one of the most important capabilities of our human visual physiology. The motion picture camera analogy provides a useful though incomplete model to help understand the process of motion perception of a moving object by the human visual physiology. In this analogy the human visual physiology presents the brain with a series of images in a manner analogous to the frames in a roll of motion picture film. The camera's frame rate is equivalent to an individual's flicker fusion frequency which varies with ambient brightness and which has been determined to vary from individual-to-individual. The brain evaluates the images on each frame and compares the evaluated images on successive frames for changes. Objects that change position between successive frames are perceived as moving. By measuring the magnitude and direction of the change in an object's position between successive frames, and knowing the interval of time between successive frames, the brain attempts to calculate the object's velocity and then predict the future location of the object in both space and time. This process works well for objects that move relatively slowly where slowly is defined by the relative motion of the object during the period of each optical frame. Such slow moving objects present a relatively distinct image in each frame with small changes in position between successive frames.
Accurate perception of fast moving objects is one of the most challenging tasks for our human visual physiology. Fast moving objects appear blurred, i.e. obscure or indistinct, because they undergo significant motion relative to their physical dimensions in each optical frame. Resolving the motion of such fast moving objects is difficult because their large relative motion in each frame creates a large uncertainty in their actual location in that frame. Since motion prediction in terms of velocity and direction is based on comparing the change in an objects position between successive frames, an increase in an object's position-uncertainty in each visual frame results in an increase in the uncertainty of its velocity between successive frames and an inability to accurately predict the future position of the object.
Accurate perception of objects moving toward us at high speed is an even more challenging task for our human visual physiology. Our ability to perceive objects moving across our field of view can be enhanced by moving our head to keep the object at the same location in the field of view. An example of this phenomena is exemplified by spectators watching a horse race. Moving our head with the moving object creates a distinct object in each frame, but causes the background to blur. However we can still resolve the motion of the object against large background objects, or in the absence of a background, use the head position information supplied to the brain from our neck muscles as when we catch a pop fly ball in baseball.
Many competitive sports include visual resolution of high speed motion as an important part of their competitive challenge. A partial list of sports that require excellent visual perception of a small fast moving object include baseball, tennis, table tennis, polo, volleyball, the goalie positions for ice hockey and soccer, and the pass receiver for football. Several other sports require a participant to maneuver while traveling along a course which requires accurate visual perception of a background that is moving fast relative to the visual frame rate of the participant. These sports include downhill ski racing and race car driving.
Accordingly the primary object of this invention is to provide a method and apparatus that enhances the ability of the human visual physiology to resolve the motion of a fast-moving object, especially one moving toward the observer, to more accurately predict the object's future position to thereby enable initiation of a more timely and more appropriate physical response to meet the challenge or threat posed by the fast-moving object.
Another important object of the present invention is to further enhance perception of an object moving at high speed by providing contrast control of the background relative to which the object is moving.
The invention possesses other objects and features of advantage, some of which, with the foregoing will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiment illustrated and described since it may be embodied in various forms within the scope of the appended claims.